Urbanization extends flight phenology and leads to local adaptation of seasonal plasticity in Lepidoptera

Urbanization is globally gaining force and challenges biodiversity but has recently also emerged as an agent of evolutionary change. Seasonal phenology and life-cycle regulation are essential processes that urbanization is likely to alter through both the urban-heat-island effect (UHI) and artificial-light-at-night (ALAN). However, how UHI and ALAN affect the evolution of seasonal adaptations has received little attention. Here, we test for urban evolution of seasonal life-history plasticity, specifically changes in the photoperiodic induction of diapause in two lepidopterans, Pieris napi (Pieridae) and Chiasmia clathrata (Geometridae). We used long-term data from standardized monitoring and citizen science observation schemes to compare yearly phenological flight curves in six cities in Finland and Sweden to those of adjacent rural populations. This analysis showed for both species that flight seasons are longer and end later in most cities, suggesting a difference in timing of diapaus...